add dockerfile for arm cross-compilation
add dockerfile for arm cross-compilation

dicej/avian,ucdseniordesign/avian,joshuawarner32/avian,lwahlmeier/avian,MaartenR/avian,lwahlmeier/avian,lostdj/avian,ucdseniordesign/avian,bigfatbrowncat/avian-pack.avian,MaartenR/avian,bigfatbrowncat/avian-pack.avian,dicej/avian,bigfatbrowncat/avian-pack.avian,ucdseniordesign/avian,MaartenR/avian,bgould/avian,minor-jason/avian,lostdj/avian,dicej/avian,ucdseniordesign/avian,marcinolawski/avian,bgould/avian,joshuawarner32/avian,lwahlmeier/avian,bgould/avian,joshuawarner32/avian,marcinolawski/avian,joshuawarner32/avian,lwahlmeier/avian,minor-jason/avian,marcinolawski/avian,minor-jason/avian,lostdj/avian,MaartenR/avian,bigfatbrowncat/avian-pack.avian,lostdj/avian,dicej/avian,minor-jason/avian,bgould/avian,marcinolawski/avian